This invention relates to an enclosed spring loaded target reel assembly for use principally with a plumb bob. It relates in particular to the structure and location of the resilient member which serves to retrieve the string. The invention is also useful for any construction project in which a straight line is required.
For years, surveyors have utilized a spring loaded target reel assembly substantially as described in U.S. Pat. No. 3,172,205. While this reel has served admirably in the surveying trade, it suffered in that the rather small overall size of the reel precluded its use in related industries such as carpentry, plumbing and the other related construction trades. Simply stated, the surveyor's reel as described in the aforesaid patent was unable to receive more than about 8 feet (21/2 meters) of usable string. Attempts to place more string on the reel required either a heavier spring or more reel space or both.
While additional reel space could have been provided by increasing the outer diameter of the reel, the addition of a longer spring posed a very real problem. The structure of the target reel in the prior art included an open inner reel with an exposed leaf spring. With the addition of the length to the leaf spring, relieving the tension on the spring during disassembly of the reel to replace the string became a rather worrisome problem. Specifically, the possibility of inadvertent removal of the lengthened spring from the open reel of the present device was felt to be unacceptable.
Accordingly, a closed reel was considered more appropriate. Further, it was felt appropriate to design the reel so that, while it was relatively easily removed from the case, it was difficult to disassemble to avoid unexpected relief of the tensioning member.
With the increased size of the reel to accept additional string and to accept the lengthened resilient member, the friction between the reel member and the case was increased to a point where rotation of the reel became somewhat difficult.
While the reel of the prior art is relatively easy to assemble, a closed reel presented a very real problem when the spring, of necessity, had to be mated with the housing so that tension could be applied to the reel while the string was being unwound from the housing.
It is a primary objective of this invention to provide a spring loaded reel for use with a plumb bob or for any other line requirement that will accept a suitable amount of string and which has an enclosed spring.
It is also an object of this invention to reduce the friction between the reel and the housing.
It is further object to provide a positive lock between the reel and the spring.
With these problems in mind, the present invention provides a reel for receiving string which comprises a case assembly, and a spool assembly. The spool assembly has a cover member and a spring member and a resilient member. The spring member is lockingly fixable within the cover member. The resilient member is substantially contained within the spring member and fixed at its first end to the case assembly and at its second end to the spring member so that rotation of the spool assembly in the case assembly will tension the resilient member.